Electrochemical reduction of halogenated organic contaminants using carbon-based cathodes: A review

Electrochemical treatment systems show promise for water treatment due to their ease of operation, modularity, and low chemical inputs. This review examines use of carbon-based cathodes within reductive electrochemical treatment systems for halogenated organic contaminants, which encompasses a vast array of contaminant classes. Due to the high electron affinity of halogen substituents, halogenated contaminants are amenable to electrochemical reduction, forming halides as harmless products, while avoiding formation of halogenated byproducts by halide oxidation. Black carbons feature a high sorption capacity for halogenated contaminants, high conductivity and low expense. Black carbon-based cathode materials enable sorption of contaminants within short hydraulic contact times and destruction of sorbed contaminants over longer timescales. This review first describes the sorptive and conductive properties of black carbons that facilitate electron transfer to halogenated contaminants. The applied voltages required to degrade halogenated contaminants, contaminant degradation rates, reaction mechanisms and final products are discussed for halogenated alkanes, alkenes, and aromatics. The effect of metal impregnation of carbon-based electrodes on dehalogenation is reviewed. Finally, this review discusses challenges with the design of black carbon-based electrodes and scaling electrochemical reactors, and future research needs.